Field of the Invention
The present invention relates generally to the fields of biomedical engineering, biochemistry, medical treatment, and surgical procedures. More specifically, the present invention provides methods, devices, and compositions for inducing changes in tissues, biomolecules, and bioactive molecules. These changes are notably useful for inducing alterations in tissues, most notably in skin, for cosmetic purposes.
Description of the Related Art
Heating of tissue is a fundamental physical event in many different medical procedures. Depending on the time-temperature history of the tissue, a cascade of physical, chemical, and biological events occurs when tissue is heated. These events can lead to a beneficial or deleterious response. One example of a beneficial response is the reduction or elimination of the appearance of skin wrinkles as a result of heat induced tissue contraction.
Skin Wrinkles
Skin wrinkles are often the consequence of advancing age and sun exposure. With increasing age and excessive sun exposure, skin quality deteriorates. This is due, in part, to changes in hydration and epidermal thickness, and on a molecular scale, to a decrease in the amount of collagen in the dermis. Further, subcutaneous fat accumulates or atrophies leading to furrowing of the skin, which produces wrinkles. In today's society, the appearance of skin wrinkles is often viewed negatively and so there is a desire in the community for a means to safely reduce or eliminate wrinkles.
Skin Rejuvenation
For many years, wrinkles have been treated with chemical peels or mechanical dermabrasion, cosmetic medical procedures in which the surface of the epidermis of the skin (the stratum corneum) is removed chemically or by abrasion (sanding), respectively. In the late 1980s, laser ablation procedures for skin resurfacing were developed and approved. Today they remain in use, but are being replaced by laser procedures that are non-ablative and less damaging to surrounding tissues. The goal of these procedures includes tissue contraction, or skin-tightening, as well as induction of a wound response that leads to the generation of new collagen, and hence, dermal thickening. In the mid to late 1990s, another cosmetic technique for skin was developed that involves a non-ablative thermal alteration to skin. This procedure, referred to as radiofrequency (RF) skin rejuvenation, is mediated through capacitive-coupling of radiofrequency energy (e.g. U.S. Pat. No. 7,189,230), using modified electrosurgical devices.
Radiofrequency rejuvenation can result in tissue contraction as tissue structural proteins and proteoglycans thermally denature and coagulate. A second effect of this procedure is a beneficial wound response causing the production of new collagen. More recently, additional devices for skin rejuvenation have been developed that employ ultrasound, high-temperature plasma directed at the tissue, or radiofrequency electromagnetic fields.
All of the current technology can result in deleterious effects in patients and create problems for the operators. For example, laser radiant energy is potentially hazardous to the operator and precautions must be made to safely contain it, and patients often report burns resulting from laser treatments.
Most radiofrequency devices work through capacitive-coupling whereby potentially hazardous electrical current passes through the patient's body, resulting in the creation of radiofrequency electric fields at the interfaces of tissues that are weak- or non-polarity. This effect capacitive coupling can lead to burns at electrodes, and inadvertent heating of collateral tissues, such as adipose tissue. This heating of collateral tissues is an undesirable consequence for skin rejuvenation that can result in atrophy, particularly in fat layers in skin during cosmetic treatments. Further, generation of smoke and charring of tissue is a common consequence of the use of electrosurgical devices. For example, during surgery, an “inadvertent capacitor” can be created between a laparoscope and the electrosurgical probe, resulting in the creation of electrical currents where they are not expected.
The instant invention eliminates the risk of charring and the generation of smoke, as it does not rely on capacitive coupling for its effects. The patient is isolated from the electrical current in the devices and no electrical current is conducted from the applicator or the patient. The invention preferably is used for the direct heating of moist conductive tissues, such as the viable dermis during cosmetic skin treatment, and less efficiently for tissues of low hydration (e.g. stratum corneum), or of low polarity (adipose), thereby providing a safer means for treating skin.
Skin Cooling
When viable tissues reach temperatures of 55 C to 60 C, tissue necrosis may occur. This is one concern during laser and radiofrequency cosmetic skin treatments. Thus, various methods of skin cooling are often employed (Anderson, R R, 2003), including the spraying of cryogen on the skin surface or on an applicator, or applying cold air, water or ice to the skin. One prior art method for the purpose of skin cooling is the application of ice cubes to the skin surface prior to laser treatment, (Gilchrest et al., 1982). These treatments have not proven entirely satisfactory, nor more importantly led to an improved therapeutic response, that is improved blanching of the port wine stain, (nevus flammeus), which is a vascular birthmark consisting of superficial and deep dilated capillaries in the skin that produce a reddish to purplish discoloration of the skin.
Other prior art attempts to provide surface cooling of the epidermis using plastic bags filled with ice placed on the skin surface for five minutes, compressed freon gas used during irradiation, or chilled water spread directly on the area being irradiated have also been explored, (Welch et al., 1983). However, these studies were done with pig cadaver tissue and normally utilized cooling periods of 2 to 14 seconds. The reported results with freon were good in only 28.5 percent of the cases, in some cases, the skin surface was momentarily frozen, and in others, the freon jet was found to overcool the skin surface.
Thus, the prior art is deficient in methods and devices for non-invasive and safer methods of skin rejuvenation induced by high frequency alternating magnetic fields that inductively heat skin tissues. The prior art is also deficient in the use of alternating magnetic fields to inductively heat conductive dermal tissues with a high degree of specificity. The prior art is also deficient in methods and devices to target during the skin rejuvenation process only conductive dermal tissue and have little effect on fat and skin surface tissues. The present invention fulfills this longstanding need and desire in the art.